"I recently bought a house, and noticed that when it rains really hard,
I get some water buildup inside of the concrete block along the edge of
the foundation... the water level is below the floor height, so it
doesn't get the floor wet. I am more concerned about mold/mildew. "
As someone else pointed out, the link doesn't allow us access to the
pics, so it's hard to tell exactly what you're talking about or seeing.
Normally, one can't see inside foundation blocks. Are you talking
about a drain, which may run around the perimeter? It's normal for
some homes to have water below the level of the floor after a rain.